In general, point at the camera. If you want to assess lighting ratios in a multi-light situation, point at each light source. There is an old method called "duplex metering method" that you may want to investigate - that is generally when one points an incident at lights rather than at the camera. Any good book on photographic exposure, especially if published around the 1950s or 60s will have such discussion. It was most often associated with flat diffusers rather than the hemisperical dome diffusers, or highly contrasty situations.